Depending on the size and weight of the wood billet being turned, each wood turner will have to determine a safe manor of securing the wood billet to the lathe. A large out of round and out of balance billet can require a secure mount if you don't want a 400 pound wood billet bouncing around the shop. A large face plate with plenty of strong screws the correct length driven into the wood billet is one of the most secure ways to secure a large wood billet for the rough turning process. Once the wood billet is rough turned and somewhat balanced you can then move on to other quicker easier means of securing the rough turned billet for the second turning and finishing. Twenty some years ago I had a 20+ pound wood billet come out of a bowl chuck on a tool catch and it bounced off the wall and ceiling and floor before it came to a stop, luckily I was standing off to one side and did not get hit, from that day forward I have used face plates for larger wood billets.